記述言語：英語   掲載種別：研究論文（学術雑誌）  

The atomic and electronic structures of NiO(001)/Au(001) interfaces were analyzed by high-resolution medium energy ion scattering (MEIS) and photoelectron spectroscopy using synchrotronradiation-light. The MEIS analysis clearly showed that O atoms were located above Au atoms at the interface and the inter-planar distance of NiO(001)/Au(001) was derived to be 2.30 +/- 0.05 angstrom, which was consistent with the calculations based on the density functional theory (DFT). We measured the valence band spectra and found metallic features for the NiO thickness up to 3 monolayer (ML). Relevant to the metallic features, electron energy loss analysis revealed that the bandgap for NiO(001)/Au(001) reduced with decreasing the NiO thickness from 10 down to 5 ML. We also observed Au 4f lines consisting of surface, bulk, and interface components and found a significant electronic charge transfer from Au(001) to NiO(001). The present DFT calculations demonstrated the presence of an image charge beneath Ni atoms at the interface just like alkali-halide/metal interface, which may be a key issue to explain the core level shift and band structure.

DOI： 10.1063/1.4820823

その他リンク： http://scitation.aip.org/content/aip/journal/jcp/139/14/10.1063/1.4820823

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevB.87.121407

その他リンク： http://prb.aps.org/abstract/PRB/v87/i12/e121407

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The elastic scattering cross sections for medium energy He ions incident on Ni, Hf and Au atoms were measured precisely using a toroidal electrostatic analyzer. We prepared the targets of Ni(similar to 1 nm)/HfO2(1.5 nm)/Si(001) and Ni(similar to 1 nm)/Au(similar to 0.5 nm)/Si(111) and performed in situ ion scattering measurement under ultrahigh vacuum condition. The absolute amounts of Ni, Hf and Au were determined by Rutherford backscattering using 1.5 MeV He ions at a scattering angle of 150 degrees. The scattering cross sections for Hf and Au were normalized by those for Ni to avoid the ambiguities of the number of incident particles, solid angle subtended by a detector, detection efficiency and the He fractions for the emerging He ions from the surfaces. The results obtained are compared with the simple Lee-Hart formula and the calculated values using the Moliere and ZBL potentials and the potentials derived from the Hartree-Fock-Slater wave functions.

DOI： 10.1016/j.nimb.2012.02.030

その他リンク： http://www.sciencedirect.com/science/article/pii/S0168583X12001449

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper reveals the fact that the O adatoms (O-ad) adsorbed on the 5-fold Ti rows of rutile TiO2(110) react with CO to form CO2 at room temperature and the oxidation reaction is pronouncedly enhanced by Au nano-clusters deposited on the above O-rich TiO2(110) surfaces. The optimum activity is obtained for 2D clusters with a lateral size of similar to 1.5 nm and two-atomic layer height corresponding to similar to 50 Au atoms/cluster. This strong activity emerging is attributed to an electronic charge transfer from Au clusters to O-rich TiO2(110) supports observed clearly by work function measurement, which results in an interface dipole. The interface dipoles lower the potential barrier for dissociative O-2 adsorption on the surface and also enhance the reaction of CO with the O-ad atoms to form CO2 owing to the electric field of the interface dipoles, which generate an attractive force upon polar CO molecules and thus prolong the duration time on the Au nano-clusters. This electric field is screened by the valence electrons of Au clusters except near the perimeter interfaces, thereby the activity is diminished for three-dimensional clusters with a larger size.

DOI： 10.1063/1.3697478

その他リンク： http://jcp.aip.org/resource/1/jcpsa6/v136/i12/p124303_s1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Despite bulk gold is one of the most inert metals in periodic table, it exhibit excellent catalytic activity in the form of nano-particles and nano-clusters. There re many disputes about the origin of such catalytic properties. While many researchers claims the importance of cluster-support interaction, some stated that catalytic properties are intrinsic for gold particles and main role in this play electronic d-band structure of which changes with decreasing the size of the particle. No experimental reports on direct measurements of d-band structure depending on size of the clusters has been published so far. Here we used electron photoemission spectroscopy coupled with medium energy ion scattering technique to investigate the d-band propertied of the gold particles depending on their size.

DOI： 10.1103/PhysRevB.83.165428

その他リンク： http://prb.aps.org/abstract/PRB/v83/i16/e165428

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Si(110) surface is considered to be a candidate for future electronic devices because of its high hole mobility. It is important to study silicide formation on this surface for device application. Here we studied initial stages of Pt silicide foemation on Si(110) by scanning tunneling microscopy (STM). We found that PtSi form of the silicide is formed and determined its epitaxial relation with underlying substrate. The silicide forms in form of 3D island. However, at certain experimental conditions it is possible to produce very long (> 1 micrometer) and aligned nanowires of PtSi on Si(110).

DOI： 10.1143/JJAP.48.08Jb11

その他リンク： http://jjap.jsap.jp/link?JJAP/48/08JB11/

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In our study it has been found that Tl atoms can migrate macroscopic distances (the width of the sample) on relatively flat Si(111) surface by applying direct current to the sample. This kind of macroscopic electromigration has never been reported before. The migrating Tl produces gradient of surface coverage resulting in different surface phases along the sample.

DOI： 10.1016/j.susc.2006.05.039

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602806006534

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Thallium is a peculiar element. Being metal of group III of periodic table, it exhibit variable valence in chemical compounds. We have studied atomic reconstructions Tl induce on Si(001) surface by low-energy electron diffraction (LEED). It has been shown the structure formed at 0.5 monolayer coverage is very similar to the typical group III metal reconstructions on Si(001), thus at this particular conditions Tl behaves as trivalent metal. The precise coordinates of the atoms were determined.

DOI： 10.1103/PhysRevB.71.245407

その他リンク： http://prb.aps.org/abstract/PRB/v71/i24/e245407

記述言語：英語   掲載種別：研究論文（学術雑誌）  

One of the problems occurred in metal-oxide field-effect transistors (MOSFET) is the diffusion of active dopants, such as boron and phosphorous from Si channel into oxide layer. This degrades the properties of insulating oxide. Introducing nitride or oxynitride buffer layer may solve the problem by trapping the diffusing dopant atoms. In the present work we have studied by density functional theory (DFT) calculations the possibility of such trapping of the boron and phosphorous by nitrogen atoms in bulk silicon.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.35848/1882-0786/ab99d1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

SiC(0001)-(1 x 1)-H consisting of monohydride is a preferred starting surface structure for synthesis of the two-dimensional materials on SiC(0001). Here we report preparation of the SiC(0001)-(1 x 1)-H by atomic hydrogen exposure and structure determination of the SiC(0001)-(1 x 1)-H by a quantitative LEED analysis. Our data show that the SiC(0001)-(1 x 1)-H is indeed a bulk terminated unreconstructed SiC(0001) surface. The sample morphology was also investigated using AFM. The dominance of one of two possible inequivalent surface terminations of 4H polytype of SiC crystal was confirmed.

DOI： 10.1103/PhysRevB.99.235434

その他リンク： https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.235434

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Local electron-phonon coupling of a one-dimensionally nanorippled graphene is studied on a SiC(0001) vicinal substrate. We have characterized local atomic and electronic structures of a periodically nanorippled graphene (3.4 nm period) prepared on a macrofacet of the 6H-SiC crystal using scanning tunneling microscopy/spectroscopy (STM/STS) and angle-resolved photoelectron spectroscopy (ARPES). The rippled graphene on the macrofacets distributes homogeneously over the 6H-SiC substrate in a millimeter scale, and thus replica bands are detected by the macroscopic ARPES. The STM/STS results indicate the strength of electron-phonon coupling to the out-of-plane phonon at the K̄ points of graphene is periodically modified in accordance with the ripple structure. We propose an interface carbon nanostructure with graphene nanoribbons between the surface rippled graphene and the substrate SiC that periodically modifies the electron-phonon coupling in the surface graphene.

DOI： 10.1021/acs.nanolett.7b00606

記述言語：英語   掲載種別：研究論文（学術雑誌）  

It was reported previously that O adatoms adsorbed dissociatively on the five-fold Ti rows of rutile TiO2(110) made the surface O-rich and reacted with CO molecules to form CO2. An electronic charge transfer taking place from gold nanoclusters to the O-rich TiO2(110) support played a crucial role to enhance the catalytic activity [Mitsuhara et al., J. Chem. Phys. 136, 124303 (2012)]. In this study, the authors have further accumulated experimental data for the CO oxidation reaction enhanced by gold nanoclusters on the TiO2(110) surface. Based on the results obtained here and previously, the authors propose an "interface dipole model," which explains the strong activity of Au nanoclusters supported on O-rich TiO2(110) in CO oxidation reaction. Simultaneously, the authors also discuss the cationic cluster model proposed by Wang and Hammer [Phys. Rev. Lett. 97, 136107 (2006)] and the d-band model predicted by Hammer and Norskov [Adv. Catal. 45, 71 (2000)]. The latter is, in particular, widely accepted to explain the activities of heterogeneous catalysts. Contrary to the d-band model, our ab initio calculations demonstrate that the d-band center for Au nanoclusters moves apart from the Fermi level with decreasing the cluster size and this is due to contraction of the Au-Au bond length.

DOI： 10.1116/1.4825117

その他リンク： http://scitation.aip.org/content/avs/journal/jvsta/31/6/10.1116/1.4825117

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Graphene nanoribbons (GNRs) were grown on n-type vicinal 6H-SiC substrates as a template, consisting of periodic nanosurface, by chemical vapor deposition (CVD). Selective growth was achieved and resulted in narrow (5-10 nm width) and millimeter-long GNRs. The GNRs contained randomly rotated domains, however, initial nuclei indicated single domain features, possibly aligned to step edges. The resistivity measurement on GNRs grown on semi-insulating SiC substrate indicated transport properties only along GNRs but no current flow across GNRs, indicating growth of electrically isolated bunches of GNRs.

DOI： 10.7567/APEX.6.055102

その他リンク： http://apex.jsap.jp/link?APEX/6/055102/

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.susc.2012.08.021

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602812003123

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We detected the H+ ions recoiled from Si(111)-1 x 1-H by medium energy 80-150 keV Ne+ impacts. The H+ fraction is dependent on emerging angle and emerging energy. With decreasing the emerging angle scaled from the surface normal the H+ fraction increases and reaches a saturation below similar to 70 degrees and almost 100% for emerging energy above 13 keV. In contrast, the charge state is not equilibrated even at similar to 85 degrees. Such strong dependence on emerging angle is due to the location of H bound by Si atoms on top of the surface. The sensitivity to H on the surfaces is estimated to be better than 5 x 10^12 atoms/cm^2 at a small emerging angle (<75), where the H+ fraction reaches similar to 100%. The unexpectedly large energy spread for the recoiled H+ spectra is attributed to the Doppler broadening caused by the zero-point energy of the vibrating H-Si system and additionally to small energy transfers among the three bodies of Ne+ and H-Si, although the assumption of binary collision between Ne+ and H is approximately valid. This H detection technique can be widely applied to analysis of chemical reactions including adsorption and desorption mediated by water and hydroxyl on various kinds of metal-oxide surfaces.

DOI： 10.1016/j.nimb.2012.01.035

その他リンク： http://www.sciencedirect.com/science/article/pii/S0168583X12000584

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The origin of the Ti 3d defect state seen in the band gap for reduced rutile TiO2(110) surfaces has been excitingly debated. The probable candidates are bridging O vacancies and Ti interstitials condensed near the surfaces. The aim of this study is to give insights into the source of the gap state via photoelectron spectroscopy combined with ion scattering and elastic recoil detection analyses.

DOI： 10.1063/1.3697866

その他リンク： http://jcp.aip.org/resource/1/jcpsa6/v136/i12/p124707_s1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Platinum nanoclusters play an important role in catalysis. The origin of the catalytic activity is the key to improve the efficiency of the catalytic processes. One of the theory explaining catalytic properties of noble metals nanoparticles states that electronic d-band structure change with the particle size is responsible for emerging catalytic activity. To find out the actual dependence of the d-band structure of Pt nanoclusters on size we carried out the experiments using medium energy ion scattering spectroscopy and electron photoemission spectroscopy.

DOI： 10.1021/jp206360e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The surface if rutile is known for its catalytic properties. In particular it can promote the reaction CO oxidation to CO2. The origin and mechanism of such a process are still debatable. Here we propose a model for such a process based on our study of the defects on rutile surface (oxygen vacancies and adatoms) studied quantitatively by medium energy ion scattering, elastic recoil detection and electron photoemission spectroscopy.

DOI： 10.1016/j.cplett.2011.07.071

その他リンク： http://www.sciencedirect.com/science/article/pii/S0009261411009055

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Titanium dioxide is an important material for many application. It is also a model material representing transition metal oxides (TMO). Despite of huge amount of studies include TiO2 as a substrate, there are still many controversy concerning its surface structure in terms of defects and defect electronic states. Here we used medium energy ion scattering and elastic recoil detection techniques to quantitatively characterize defects (mainly oxygen vacancy and oxiygen adatoms) depending on sample preparation conditions.

DOI： 10.1016/j.nimb.2011.05.007

その他リンク： http://www.sciencedirect.com/science/article/pii/S0168583X1100509X

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Conventional graphene growth on SiC surface are performed by thermal decomposition of the surface at high temperatures (>1100 degree C), this , however, not always desirable. We have shown the method of producing graphene on SiC surfaces by Ni-silicidation reaction at lower temperatures (~800 degree C). The characteristics of resulting graphene layers has been analysed by various of techniques. Interestingly graphene thickness depends on the SiC crystal orientation. While on (000-1) surface monolayer graphene can be grown by this technique, on (0001) surface double layer graphene grows.

DOI： 10.1016/j.susc.2010.05.019

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602810002219

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Si surface hydrogenation is an important process for application. Hydrogen can passivate the surface, play role of a surfactant in epitaxial growth of metals and so on. While hydrogenation of the Si(111) and Si(001) surfaces is well studied it is not the case for Si(110). While many researchers concentrated in developing technique of chemical hydrogenation, it is very interesting what happening when H atoms arrive at the clean surface in vacuum. Here we found a new surface structures which formed by in situ atomic hydrogen exposure on Si(110) surface. The surfaces have been analyzed by scanning tunneling microscopy (STM).

DOI： 10.1143/JJAP.49.08LB05

その他リンク： http://jjap.jsap.jp/link?JJAP/49/08LB05/

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The quantitative analysis of hydrogen containing on the surface and near the surface is of high importance for science and application in the hydrogen related catalysis field and surface science. Being extremely light and small element hydrogen is difficult to observe by techniques conventionally used for surface composition and structure analysis. Here we have shown that it is possible to perform quantitative analysis of the H amount on the surface by high resolution elastic recoil spectroscopy using Ne ions beam. Hydrogen vibration characteristics can also be deducted from recoil energy spectrum.

DOI： 10.1016/j.susc.2010.05.018

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602810002207

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Nanometer scale metal particles are subject of very intensive studies because of its application in catalysis. Bi-metallic core-shell structures are expected to be even more effective than mono-metallic particles. It is however extremely difficult to study the structure of such particles by usual methods, because core material is covered by the shell ind not directly accessible. Only high-resolution transmission electron microscopy can give an insight on such particle structure, which, however, lacks statistical nature. We have shown that medium energy ion scattering technique (MEIS) is capable of analyzing such core-shell structure with good precision on the example of Au/Pd core-shell particles.

DOI： 10.1016/j.nimb.2010.03.032

その他リンク： http://www.sciencedirect.com/science/article/pii/S0168583X10003083

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Despite the fact that gold is the most inert metal of periodic table, it shows excellent catalytic properties in form of nanoparticles. The origin of such catalytic activity of gold is a subject of furious debates. One of the possible explanation is a charge transfer occurred on the interface between gold particles and underlying substrates. Here we studied experimentally the electronic charge transfer between gold particles and titanium dioxide and STO by medium energy ion scattering and photoemission spectroscopy.

DOI： 10.1016/j.susc.2009.12.024

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602809008012

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Surface silicides are very important in device applications. Depending on properties of particular silicide it can form ohmic or Schottky junction with Si substrate. Platinum is an important material both for the production of semiconductor devices and in the field of catalysis. In the present work we studied different surface structures formed by Pt on the top of Si(110) surface. Si(110) surface is not so well studied especially in terms of metal adsorption comparing to (001) or (111) Si surfaces. It is, however, posses some advantageous properties such as increased hole mobility. Series of Pt surface reconstructions formed at different coverage have been observed by scanning tunneling microscopy (STM) formed on Si(110) for the first time.

DOI： 10.1016/j.apsusc.2008.01.124

その他リンク： http://www.sciencedirect.com/science/article/pii/S016943320800189X

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Identical clusters with enhanced stability called magic clusters. Magic clusters formed on Si(111) -(7x7) surface represent extremely dense regular array of zero-dimension structures which potentially can be utilized in different high-density memory or electronic devices. In the present work we studied formation of Tl magic clusters faulted half-unit cell of Si(111)-(7x7). Interestingly the cluster exhibit locally 2x1 structures.

DOI： 10.1016/j.apsusc.2008.01.141

その他リンク： http://www.sciencedirect.com/science/article/pii/S0169433208001943

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Several unconfirmed models of tin c(8x4) and (5x1) reconstruction on Si(100) existed so far. We applied scanning tunneling microscopy and coaxial impact collision ion scattering spectroscopy (CAICISS) to distinguish which model is correct.

DOI： 10.1016/j.susc.2008.03.009

その他リンク： http://www.sciencedirect.com/science/article/pii/S0039602808001684

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Indium produces the overlayer structure on Si(111) surface which undergoes a phase transition at low temperature. We have studied electronic and atomic structure of this phase by scanning tunnleing microscopy (STM) and low-energy electron diffraction (LEED) and proposed the mechanisms driving such reversible phase transition.

DOI： 10.1103/PhysRevB.74.035436

その他リンク： http://prb.aps.org/abstract/PRB/v74/i3/e035436

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The stability of N-B and N-P atomic complexes in bulk silicon has been studied by density functional theory (DFT) calculations, as well as changes of electronic properties of active dopants by forming such complexes. This work shows that it is possible to provide nitride or oxinitride buffer layer between doped Si channel and insulating gate oxide to prevent parasitic diffusion of active dopants into the oxide layer. Dopants such as boron and phosphorous are trapped by nitrogen atoms. Formation of such complexes makes the dopants inactive.

開催年月日： 2015年12月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Hilton Niseko Village Hotel, Hokkaido   国名：日本国  

その他リンク： http://dora.bk.tsukuba.ac.jp/event/ICSPM23/

開催年月日： 2014年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Fukuoka University, Fukuoka   国名：日本国  

The electronic contact between metal and oxide is an important issue in terms of oxide electronics, which has recently attracted much attention. It has been also revealed that electronic charge transfers between metal and oxide supports play a crucial role in catalytic activities, in particular, for Au nano-particles on oxide supports. NiO is one of the most frequently utilized supports in catalysis and a model transition oxide. Indeed, Au nano-particles grown on NiO supports work well as catalyst in CO oxidation and other reactions. Although there are a number of reports on NiO/Ag interface, Au interaction with NiO stays much out of focus, in spite of its importancy. In the present work the atomic and electronic structures of NiO(001)/Au(001) interface were analyzed by medium-energy ion scattering spectroscopy, (MEIS), photoelectron spectroscopy (PES) and DFT calculations. We first revealed by MEIS that the O atoms were located above Au atoms at the NiO(001)/Au(001) interface (Fig. 1). This was supported by the DFT calculations. Concerning the electronic properties of the NiO/Au interface, we observed metallic features for NiO(001)/Au(001) for NiO thickness up to 3 ML. Relevant to the metallic features, the bandgap decreased with decreasing the NiO thickness from 10 down to 5 ML. We also observed the interface component for Au 4f core level, which shifted by 0.35 eV to higher binding energy side compared with that for bulk Au. Despite that, the DFT calculations demonstrated no significant charge transfer. We, however, found out the presence of image charge beneath the Ni atoms at the NiO(001)/Au(001) interface (Fig. 2), which may be a key issue to explain the core level shift and band structure.

その他リンク： http://www.iumrs-ica2014.org/

開催年月日： 2024年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：Tokyo City University   国名：日本国  

開催年月日： 2024年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

開催年月日： 2023年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tohoku University   国名：日本国  

Graphene can be grown on or transferred onto a variety of substrates, including those with natural or artificial 1D topographic features. This may result in 1D periodic strain fields created in graphene sheet. Modification of electronic structure of graphene by applying strain has been long researched topic in 2D material science. It was shown that strain field may results in electron behaviour similar to the one in magnetic field [1]. Such pseudo-magnetic field (PMF) can reach extremely high values and be localized in nanometer scales. There has been several reports of observation of 1D nanoscaled PFM in rippled graphene [2,3]. However, the rusults interpretation is not unambiguous and rise some questions. In the present work we employ atomistic tight-binding calculations to study electronic structure of 1D strained graphene with various strain profiles and compare them to ones with artificial external magnetic field of similar configuration to pinpoint similarities and important differences (ex. in Fig.1). The results may provide useful insights for experiment data interpretation.

開催年月日： 2023年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

Modification of electronic structure of graphene by applying strain has been long researched topic in 2D material science. It was shown that strain field with triangular symmetry results in electron movement in graphene like those in magnetic field resulting in Landau quantization of electron energy levels [1]. While creating truly triangular strain fields for uniform pseudo magnetic field (PMF) may be difficult to achieve experimentally, there are attempts to create 1D ripple structures to induce 1D periodic PMF in graphene [2]. Interestingly, applying simple PMF for 1D strain along zigzag edge direction in graphene results in zero PMF, the flat band quasi-Landau levels are still formed in full tight-binding calculations although in a very different manner compared in classical Dirac fermion system in magnetic field (Fig. 1). In the present work we perform tight-binding calculations with band unfolding for various 1D periodic strain fields in graphene and discuss the results in the paradigm of possible pseudomagnetic and pseudoelectric fields and their applicability for description of resulting band structure modifications.

開催年月日： 2021年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

Twisted bilayer graphene has been a hot topic in recent years due to very intriguing electronic band structure, strongly correlated electron states, and superconductivity. Most studies are concentrated on effective tight-binding model withing supercell Brillouin zone of free-standing layers. This, however, often difficult to relate to experimental observations. Here we report full atomistic tight-binding calculation results on twisted bi- and trilayer graphene with asymmetric layer doping, which is more closely related to experimental condition of epitaxial and transferred graphene layers on SiC, and unfolded in momentum space realistically measured by ARPES. As seen from Fig. 1 the results of these calculations are in excellent agreement with experimental data, which allow us to fine tune the parameters of the model, explore and predict the influence of various factors such as interlayer distance, and doping difference on minigaps and flat band formation.

開催年月日： 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

Twisted bilayer graphene (TBG) is the topic which have exploded the field of 2D materials thanks for promising correlated physics and room-temperature superconductivity. However, in spite of massive theoretical background, the experimental results are still difficult to produce. We have developed the method of producing TBG of sub-mm scale with good and clean interface which is accessible for investigation using conventional surface science techniques, such as ARPES and LEED. To interpret the results extensive modelling is required specifically aimed to be comparable with experimental data. Here we present our recent advancements on modelling band structure of TBG in comparison with ARPES and structural relaxation in relation to SPA-LEED observations.

開催年月日： 2020年9月 - 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：online   国名：日本国  

Graphene is a fascinating 2D material. However, due to small spin-orbit interaction (SOI) in carbon atoms, band spin polarization is usually very small in normal graphene layer, which limits its use for spintronics devices. Sn is a heavy group IV element with substantial SOI, and it would be interesting to see if 2D materials made of Sn are possible to be realized and what properties they would exhibit. In our work we address the issue of stability and electronic properties of 2D Sn layers on SiC(0001) by ab initio calculations and experimental measurements. Our DFT calculations show that layer with honeycomb structure similar to graphene (it is called stanene in case of Sn atoms) is stable when grown on top of Si2N3/SiC(0001), while on bare SiC(0001) the more dense (1x1), unusual for group IV element, triangular structure has better energy stability. While growth of 2D triangular structure on bare SiC can be hindered by thermal growth dynamics and result in clustering, one of the solution would be to intercalate Sn atoms into graphene/SiC(0001) interface, which suppresses 3D growth and promote layered. This approach was realized experimentally with a very good agreement between experimental results and computational data [1,2]. Both triangular and honeycomb structures are found to have very interesting band dispersion with spin-polarized states in form of Rashba and Zeeman splitting.

その他リンク： https://fntg.jp/jp_new/symposium/sympo59/index_e.html

開催年月日： 2020年3月

記述言語：英語  

開催地：Nagoya University   国名：日本国  

Twisted bilayer graphene attracts the attention of surface science community lately due to prospects of isolated flat band formation at specific small twist angles and, as a consequence, strongly correlated electron behavior, including possible superconducting state. Most theoretical works to this date are concentrating on using free standing bilayer model without doping and evaluated using continuum tight-binding approximation due to extreme size periodic structure. While without doubt a powerful tool, this simplified model may miss some of the phenomena caused by local interlayer interactions. Here, we report on analysis of the band structure using direct universal large atomistic simulation by Slater-Koster type tight-binding model with subsequent band unfolding for asymmetrically doped graphene multilayers which may provide results unforeseen by previous approaches. The reduction of the Fermi velocity and formation of minigaps is obvious from calculations. Moreover adding more alternatively rotated layers reduces the band width even more as shown.

開催年月日： 2019年9月 - 2020年9月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Gifu University   国名：日本国  

Perfect and sharp interface between semiconductor and oxide is crucial for performance of MOSFET devices. Thin, high-k epitaxial oxides on SiC(0001) are especially interesting as they are difficult to grow while maintaining the amount of interface states at minimum. Recently, we have found that aluminum oxide can be grown epitaxially on SiC(0001) exhibiting new (3√3×3√3) structure. Our XPS and X-CTR scattering profile analysis show that this oxide film consist of two alumina layers, with composition and interlayer distances close to those of α-Al2O3(0001) and γ-Al2O3(111). The accurate structure of alumina is still a controversial topic however, especially in the form of thin layers, where exotic precursor structures have been observed [1]. In the present study, based on our previous experimental data, we try to build and analyze the atomic and electronic structure of this epitaxial alumina layer using ab initio and tight binding computational approaches.

開催年月日： 2019年9月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Doshisha University, Kyoto, Japan   国名：日本国  

It is known that electronic properties of graphene, in particular the existence of band gap in electronic band structure, can be altered by external periodic potential and periodic geometric and atomic modifications of graphene sheet. It has been shown also, that to create a noticeable effect, these modifications has to be very precise and relatively short ranged. The only reliable way to produce such effects is the use of self-organization and specific substrates. SiC(1-100) surface (so called m-plane) is a good candidate as it consists of short-ordered 1D periodic structure (1 nm for 4H- and 1.5 nm for 6H-SiC) of alternating Si- and C-terminated facets with corrugation of ~1.7 Å. Unfortunately, the lattice mismatch does not allow the full utilization of this short-ordered periodicity, but still, different options are available. Here we investigate atomic and electronic structure of various possible configurations of graphene on m-plane of SiC by DFT-based tight-binding calculations (DFTB). One of the investigated configurations is shown in Fig.1. Interestingly, a significant band gap in graphene’s electronic structure is obtained in such a case.

開催年月日： 2019年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：TU Chemnitz   国名：ドイツ連邦共和国  

開催年月日： 2019年8月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：TU Chemnitz   国名：ドイツ連邦共和国  

開催年月日： 2019年8月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：TU Chemnitz   国名：ドイツ連邦共和国  

開催年月日： 2019年3月

記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Kyushu University, Fukuoka   国名：日本国  

It has been shown recently that twisted bilayer graphene (TBG) possesses some unique electronic properties such as Mott-insulator state, superconducting state, and quasicrystalline orders depending on twisting angle. The properties vary considerably even with small angle variation. Here we report computational study results of electronic and atomic structures (which has not been addressed before to our knowledge) of TBG at certain angles achievable in practice for large area graphene sheets in our previous experiments. The calculation of TBL is extremely difficult due to structural incommensurability between layers in general and huge unit cell even in periodic cases for angle <10o. Here we try to utilize DFTB (DFT-based tight binding) method for cluster calculation of large TBL chunks. The results are puzzling. While interlayer distance seems not to be modulated to noticeable degree between regions with AA and AB stacking, the layers try to readjust rotation angle to minimize the interaction energy, resulting in possible slight twist deformation of graphene lattice and new more favorable average twisting angle (Fig.1).

開催年月日： 2018年3月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Tokyo University of Science, Tokyo   国名：日本国  

Two-dimensional (2D) materials are one of the attention centers of material science due to their fascinating physical properties and potential device application. Most of the efforts are applied towards materials with honeycomb, graphene-like lattice grown on metallic or semiconducting substrates, while 2D overlayers with different lattice, namely triangular ones, may exhibit Dirac-cone like electron dispersion and interesting spin-splitting of states due to larger than carbon spin-orbit interaction. Here, we investigate the possibility of formation of 2D dense triangular atomic lattices layers (TLAL) of different group III, IV, and V elements on SiC(0001) surface [Fig.1(a)] and their electronic structure by means of DFT calculation. We found that In [Fig.1(b)] and Pb triangular structures are stable on SiC(0001) (planar configuration for In and buckled for Pb), while for Tl and Bi it is controversial. The spin-polarized Dirac-cone electron dispersion of In, shown in Fig.1(c), makes it interesting it terms of application in spintronic devices.

開催年月日： 2017年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Iwate University   国名：日本国  

Two-dimensional (2D) materials are one of the attention centers of material science due to their fascinating physical properties and potential device application. Most of the efforts are applied towards materials with honeycomb lattice such as graphene, silicene, germanene and similar. 2D material with other lattices could be of Dirac type. One of such possible atomic lattices is a triangular one. Our experimental results and calculations points out on possibility to form dense (1x1) triangular lattice atomic layers (TLAL) of heavy group IV elements (Sn, Pb) that has not been reported before. Here we present our ab initio calculations showing properties of such TLALs on bare SiC(0001) and at graphene/SiC(0001) interface. Non-trivial bonding configuration in this 2D layers results in formation of perfect 2D metal. It also exhibits Dirac-cone-like electron dispersion features. Owing to large spin-orbit interaction (SOI), these layers show both Rashba- and non-Rashba-type of spin-polarization of electron bands at high symmetry points and also may induce spin-polarization in electronic structure of graphene layer.

開催年月日： 2017年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Fukuoka International Congress Center, Fukuoka   国名：日本国  

Two-dimensional (2D) materials are one of the attention centers of material science due to their fascinating physical properties and potential device application. Most of the efforts are applied towards materials with honeycomb lattice such as graphene, silicene, germanene and similar. This is because of interesting physics of Dirac fermions. It was shown, however, that Dirac-like electron dispersion is possible in non-honeycomb lattices [1, 2], however the studies of non-honeycomb lattice 2D materials are rather rare up to date. One of such possible atomic lattices is a triangular one. Triangular lattices of heavy group IV elements has been addressed previously in a context of Mott-insulator and topological-insulator state of sparse (√3x√3) adatom reconstruction on hexagonal surfaces of SiC(0001)[3] and Si(111)[4]. Dense (1x1)-type lattices, where metal atoms are directly interacting through in-plane bonding (Fig. 1a), are not reported. Here we present our ab initio calculations and experimental results showing that such triangular atomic lattices of Ge, Sn and Pb could be stable on SiC(0001), and especially at graphene/SiC(0001) interface. Non-trivial bonding configuration in this 2D layers results in formation of perfect 2D metal. It also exhibits Dirac-cone-like electron dispersion features. Owing to large spin-orbit interaction (SOI), these layers show both Rashba- and non-Rashba-type of spin-polarization of electron bands at high symmetry points in the Brillouin zone simultaneously (Fig. 1b) which has not been observed before and represents an interesting case both for science and possible application in spintronic device application.

開催年月日： 2017年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Osaka University   国名：日本国  

Graphene's nanostructures such as nanoribbons (GNRs) attract a great interest due to peculiar quantum effects and possibility to open a band gap in graphene’s electronic structure - a condition required for graphene utilization in switching logic electronic devices. It is challenging task to produce GNRs with good control over width and orientation on semiconducting substrate. Previous reports have shown that GNRs could be selectively grown on high-index facets of SiC(0001) surface, albeit the width of such GNRs was relatively wide. Here, we report a development of a method to grow periodic arrays of very narrow GNRs (width ~1.6 nm) with armchair edge structure and sizable band gap (several hundred meV) and 1D structurally modulated graphene layers on large facets (induced by step bunching) of vicinal SiC(0001) surfaces by high-temperature annealing in Ar atmosphere. We present observations and analysis of atomic and electronic structures of these nanomaterials by means of scanning tunneling microscopy (STM) and spectroscopy (STS).

開催年月日： 2016年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Kanazawa University   国名：日本国  

Large scale graphene production for device application preferably has to be done directly on substrates it will be used on (such as SiC). The strong coupling between graphene and substrate surface results in significant degrading of graphene's properties. One of the possible ways to overcome this problem and acquire additional control over electronic properties of graphene is to modify the interface atomic structure between graphene and substrate. As seen from calculations graphene’s band structure has crucial dependence on periodicity and location of influential interface atoms. On the other hand, STM shows large variety of possible Si-induced interface structures produced by intercalation in graphene/SiC(0001) system. Although many of the interface structures are still unknown, here we tried to track what influence they may have on graphene electronic bands by means of calculation of simplified models based on STM observations.

開催年月日： 2016年3月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Tohoku GAkuin University, Sendai   国名：日本国  

開催年月日： 2015年9月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Kansai University, Osaka   国名：日本国  

It is well known that graphene is a zero-gap semiconductor, thus it is difficult to apply it directly as an alternative to classical semiconductors in technological application despite its outstanding mechanical and carrier mobility characteristics. However, the introduction of even weak periodic potential may change graphene electronic properties significantly (see Fig.1 for example). It may influence graphene sheet doping level as well as open a band-gap in its electronic structure. Such potential may be represented by underlying atoms of the interface structure between graphene and substrate bonded to graphene or step structure of the substrate itself. Here we show that electronic structure changes caused by interface atoms influence are strongly dependent on periodicity of interface structure with respect to graphene lattice and site of influence. We discuss the possible interface structures between graphene and SiC substrate caused by atoms intercalation based on theoretical calculations and experimental observations.

開催年月日： 2015年3月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Waseda University, Tokyo   国名：日本国  

Epitaxial growth on SiC substrate is a promising method of large-scale graphene production as graphene can be relatively easy formed on this surface by thermal decomposition, and there is no need for transfer process. The first graphitic layer formed on SiC, however, strongly interacts with the substrate. This can be used to tune graphene properties by creating suitable interface structures on SiC surfaces by means of atoms intercalation. Here, we have studied Si intercalation into graphene/SiC interface. It turns out, that variety of Si structures can be formed depending on Si coverage. The STM appearance of these structures is strikingly similar to that of Si overlayers formed on clean SiC. Unfortunately, most of the structures Si form on clean SiC surface are metastable (except for √3 and 3x3) and not well studied. Moreover, partially decoupled graphene exhibit structural shift with respect to the underlying interface structure, which may result in local differences in graphene electronic structure (Fig.1b,c). In the present work we have studied the interaction of graphene with Si interface structures by means of STM and DFT calculations.

開催年月日： 2014年9月 - 2014年10月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Far Eastern Federal University, Vladivostok   国名：ロシア連邦  

Large-scale graphene epitaxy on SiC substrates is considered to be very promising for future graphene-based electronic devices production. The first graphitic layer on-top of SiC substrate takes form of a buffer layer with periodicity of (6√3x6√3) and loses its characteristic linear energy dispersion as well as advantageous extremely high carrier mobility. This emphasizes the influence of a substrate on graphene properties. In order to eliminate undesired substrate effects and tune graphene layer properties to our needs the interface between graphene and SiC can be modified by different elements intercalation. The most popular, as of today, is hydrogen intercalation which decouples graphene layer from the SiC substrate. Data on other elements intercalations are reported mainly based on theoretical predictions. Here, we present the experimental as well as computational results on Si intercalation into graphene/SiC interface. We have found that, depending on the amount of intercalated Si, different structures are formed at the interface. Most interestingly, all the structures are similar to those stable and metastable ones formed by excess of Si on clean SiC surfaces. In most cases the graphene layer decouples from the substrate and show characteristic linear band dispersion. The interface structures are analyzed by STM and modelled using DFT calculations.

その他リンク： http://ntc.dvo.ru/apsss-1/

開催年月日： 2014年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Chubu University, Kasugai, Aichi   国名：日本国  

Epitaxial graphene on SiC substrate looks very promising in terms of technological application. Unfortunately, first graphitic layer grown on SiC takes form of buffer layer and looses graphene-specific electronic properties owing to strong graphene-substrate interaction. Intercalating different materials into graphene/SiC interface may decouple graphene layer and tune its electronic properties. Nowadays, hydrogen intercalation is widely used for this purpose. There are some reports (mainly computational studies) on the other elements intercalation. Here, we present the experimental as well as computational results on Si intercalation into graphene/SiC interface. We have found that, depending on the amount of intercalated Si, different structures are formed at the interface. The structures are similar to those stable and metastable ones formed by excess of Si on clean SiC surfaces. In most cases the graphene layer decouples from the substrate and show characteristic linear band dispersion. The interface structures are analyzed by STM and modelled using DFT calculations.

開催年月日： 2014年8月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Fukuoka University, Fukuoka   国名：日本国  

Graphene nanoribbons (GNRs) attract a lot of attention not only because of possible applications to future electronic devices but also edge induced unique electronic characteristics. We have fabricated GNRs by epitaxial growth on self-ordered vicinal SiC surfaces (1). In this presentation we show the results of micro-Raman spectroscopy study of such GNRs in terms of electron-phonon interactions at nanoribbon edges. The GNRs were grown on vicinal SiC surfaces (miscut toward [1-100]) by molecular-beam epitaxy (MBE) using solid carbon source (2). Figure 1 shows AFM images (phase-mode) of the surface after (a) 20 and (b) 100 min growth. Graphene islands selectively grow on (0001) terraces and evolve along [11-20] direction to form GNRs. Figures 2(a) and (b) show polarized Raman spectra of D- and G-band region after each growth shown in Fig. 1(a) and (b), respectively. 0 (90) degree corresponds to laser polarization angle with respect to the step edge direction. Figure 2(a) indicates almost no polarization dependence whereas strong reduction of the D-band intensity is observed in Fig. 2(b). This is attributed to the dominant armchair edge character of our GNRs (3). Note the presence of ~ 4cm-1 shift in the D-band peak position. It is speculated that this shift is caused by a new type of phonon mode, softened and localized at the arm-chair edges (edge phonons).

その他リンク： http://www.iumrs-ica2014.org/

開催年月日： 2014年3月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Tokai Univiersity   国名：日本国  

Graphene proved to be one of the most exciting materials in terms of scientific and technological importance. Unfortunately, first graphitic layer grown on SiC takes form of buffer layer and looses graphene-specific electronic properties owing to strong graphene substrate interaction. Hydrogen intercalation may decouple graphene from the substrate [1]. It is, however, interesting to check if other elements intercalation takes place in graphene/SiC interface and how it affects graphene properties. Silicon is one of such possible materials. Moreover, there are reports of graphene-like silicone 2D structure, named silicene [2]. And confined region of the graphene/SiC interface is a possible place to grow such 2D material. Accessing the properties of such interfacial layer in experiments is difficult, so in the present work we investigate its atomic and electronic structures by means of first-principals and classical molecular dynamics calculations. We have also performed initial experiments with silicon intercalation in graphene/SiC interface and study the resultant structures by STM.

開催年月日： 2013年8月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Yaroslavl' University, Yaroslavl'   国名：ロシア連邦  

その他リンク： http://isi2013.spbstu.ru/

開催年月日： 2013年3月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Hiroshima University   国名：日本国  

開催年月日： 2012年9月

会議種別：口頭発表（一般）  

開催地：University of Tokyo, Tokyo   国名：日本国  

開催年月日： 2012年9月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Yokohama National University   国名：日本国  

開催年月日： 2011年8月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Vladivostok   国名：ロシア連邦  

開催年月日： 2011年6月

会議種別：口頭発表（一般）  

開催地：Université de Pierre et Marie Curie, Paris   国名：フランス共和国  

開催年月日： 2011年6月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Université de Pierre et Marie Curie, Paris   国名：フランス共和国  

開催年月日： 2010年11月

会議種別：口頭発表（一般）  

開催地：Boston   国名：アメリカ合衆国  

開催年月日： 2010年9月

会議種別：口頭発表（一般）  

開催地：Institute of Automation and Control Processes, Vladivostok   国名：ロシア連邦  

開催年月日： 2009年12月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Atagawa   国名：日本国  

開催年月日： 2009年11月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Kyoto   国名：日本国  

開催年月日： 2008年12月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Atagawa   国名：日本国  

開催年月日： 2008年10月

会議種別：口頭発表（一般）  

開催地：Tohoku University, Sendai   国名：日本国  

開催年月日： 2008年8月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Vladivostok   国名：ロシア連邦  

開催年月日： 2007年11月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Tokyo   国名：日本国  

開催年月日： 2006年10月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Kashiwa   国名：日本国  

開催年月日： 2006年9月

会議種別：口頭発表（一般）  

開催地：Institute of Automation and Control Processes, Vladivostok   国名：ロシア連邦  

開催年月日： 2005年11月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Omiya   国名：日本国  

開催年月日： 2004年10月

会議種別：口頭発表（一般）  

開催地：Toyama University, Toyama   国名：日本国  

開催年月日： 2002年10月

会議種別：口頭発表（一般）  

開催地：Institute of Automation and Control Processes, Vladivostok   国名：ロシア連邦